1. Field of the Invention
The present invention relates to a spraying device suitable for spraying a plurality of liquids in one direction for use, for example, in cleaning a workpiece such as a semiconductor wafer, a glass substrate, or the like which needs to be cleaned to a high degree of cleanliness.
2. Description of the Prior Art
In the process of fabricating semiconductor wafers, it has been the customary practice to employ various cleaning methods for removing foreign matter such as fine particles of semiconductor materials, dust particles, crystalline protrusions, etc. from the surfaces of semiconductor wafers.
One of such cleaning methods is a scrubbing process as shown in FIG. 6 of the accompanying drawings. According to such scrubbing process, a cleaning liquid is ejected from spraying devices 2 to surfaces of a workpiece 1 such as a semiconductor wafer while at the same time cleaning elements 3 such as brushes, sponges, etc. are rubbing the surfaces of the workpiece 1.
FIG. 7 of the accompanying drawings illustrates the structure of the spraying device 2 in detail. The spraying device 2 comprises a plate-like body 4 having a fluid passage 5 defined therein and a linear array of orifices 6 communicating with the fluid passage 5, orifices 6 being spaced at a predetermined pitch in the longitudinal direction of the fluid passage 5. In use, a cleaning liquid is introduced into the fluid passage 5 and is ejected through the orifices 6.
Since this spraying device 2 can be supplied with only one type of cleaning liquid at a time, if a chemical solution and pure water are to be applied from the spraying device 2 to the same workpiece 1, then the chemical solution and the pure water are introduced alternately into the fluid passage 5. When the chemical solution is introduced into the fluid passage 5, it contaminates the fluid passage 5 and the orifices 6 from which the pure water is to be ejected in a successive cycle. Therefore, it is necessary to wash the residual solution out of the fluid passage 5 and the orifices 6 by subsequently supplying pure water to minimize the possibility of contaminating the workpiece 1, which means that a longer cleaning period is necessary by using the pure water. Even by doing so, it is still difficult to completely remove the remaining chemical solution to null the possibility of contaminating the workpiece 1.
One solution for the above problem is to provide two spraying devices 2 for spraying the chemical solution and the pure water, respectively, positioned above and below the workpiece 1. Such a cleaning system, however, needs a relatively large installation space. It may not be easy to locate one or both of the two spraying devices 2 for spraying the chemical solution and the pure water, respectively, in a region close enough to clean the workpiece 1 efficiently.